Non-volatile memory device

ABSTRACT

Memory devices are disclosed. In an embodiment of the disclosed technology, a memory device may include a substrate including an active region, and a first floating gate, a second floating gate, a third floating gate and a fourth floating gate formed on the substrate, arranged to partially overlap with the active region. The first floating gate and the third floating gate are arranged in a first direction at one side of the active region and asymmetrical about a center of the active region, and the second floating gate and the fourth floating gate are arranged in the first direction at another side of the active region and asymmetrical about the center of the active region.

CROSS-REFERENCES TO RELATED APPLICATION

This patent document claims the priority and benefits of Korean patentapplication number 10-2020-0187100, filed on Dec. 30, 2020, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The technology and implementations disclosed in this patent documentgenerally relate to a semiconductor device.

BACKGROUND

The growing trend of using mobile devices to access information anytimeand anywhere has increased the demand for highly integratedsemiconductor devices. System-on chip (SoC) is the technology thatintegrates several computer components into one semiconductor device.SoC technology makes it possible to fabricate memory and non-memory on asingle chip.

Embedded memory is the most sought after by many industries. Embeddedmemory is an on-chip memory integrated into an SoC that supports logiccircuits on the SoC to perform intended functions. One example of theembedded memory is an electrically erasable programmable read onlymemory (EEPROM). The EEPROM can retain data in absence of power like aread only memory (ROM), and can be erased and reprogrammed through theapplication of a high voltage.

SUMMARY

The embodiments of the disclosed technology relate to a non-volatilememory device with improved reliability.

In some embodiments of the disclosed technology, a memory device mayinclude a substrate including an active region, and a first floatinggate, a second floating gate, a third floating gate and a fourthfloating gate formed on the substrate, arranged to partially overlapwith the active region. The first floating gate and the third floatinggate are arranged in a first direction at one side of the active regionand asymmetrical about a center of the active region, and the secondfloating gate and the fourth floating gate are arranged in the firstdirection at another side of the active region and asymmetrical aboutthe center of the active region. The first floating gate and the secondfloating gate are arranged to face each other in a second directionperpendicular to the first direction, and the first floating gate isasymmetrical from the second floating gate, and the third floating gateand the fourth floating gate are arranged to face each other in thesecond direction, and the third floating gate is asymmetrical from thefourth floating gate.

In some embodiments of the disclosed technology, a memory device mayinclude a substrate, first and second well regions formed in thesubstrate and having different conductive types, the first and secondwell regions arranged parallel to each other in a first direction, anisolation layer formed in the substrate to define a first active regionand a second active region in each of the first and second well regions,first and second selection gates formed on the substrate and structuredto overlap with the first active region, the first and second selectiongates arranged parallel to each other in a second directionsubstantially perpendicular to the first direction, and the first andsecond selection gates having a linear shape extending in the firstdirection, and first and second floating gates arranged adjacent to thefirst and second selection gates, respectively, the first and secondfloating gates overlapping with the first active region and the secondactive region, and the first and second floating gates facing each otherin the second direction. The first floating gate and the second floatinggate face each other in the second direction and are asymmetrical fromeach other.

In some embodiments of the disclosed technology, the memory device mayfurther include a third well region formed at the substrate, the thirdwell region having a conductive type substantially the same as theconductive type of the first well region, a third active region definedin the third well region by the isolation layer, the third active regionoverlapping with the first selection gate and the second selection gate,and third and fourth floating gates arranged adjacent to the first andsecond selection gates, respectively, the third and fourth floatinggates overlapping with the third active region and the second activeregion, and the third and fourth floating gates facing each other in thesecond direction. The third floating gate and the fourth floating gateface each other in the second direction and are asymmetrical from eachother.

In some embodiments of the disclosed technology, a non-volatile memorydevice may include a substrate, a first floating gate, a second floatinggate, a third floating gate and a fourth floating gate. The substratemay include an active region. The first to fourth floating gates may beformed on the substrate. The first to fourth floating gates may beradially arranged to be partially overlapped with the active region. Thefirst floating gate and the third floating gate may face each other in afirst direction. The first floating gate and the third floating gate mayhave asymmetrically planar shapes. The first floating gate and thesecond floating gate may face each other in a second directionsubstantially perpendicular to the first direction. The first floatinggate and the second floating gate may have asymmetrically planar shapes.The third floating gate and the fourth floating gate may face each otherin the second direction. The third floating gate and the fourth floatinggate may have asymmetrically planar shapes. The fourth floating gate andthe second floating gate may face each other in the first direction. Thefourth floating gate and the second floating gate may haveasymmetrically planar shapes.

In some embodiments of the disclosed technology, a non-volatile memorydevice may include first and second well regions, a device isolationlayer, first and second selection gates and first and second floatinggates. The first and second well regions may be formed at a substrate.The first and second well regions may have complementary conductivetypes. The first and second well regions may be arranged parallel toeach other along a first direction. The device isolation region may beformed at the substrate to define a first active region in the firstwell region and a second active region in the second well region. Thefirst and second selection gates may be formed on the substrate. Thefirst and second selection gates may be overlapped with the first activeregion. The first and second selection gates may be arranged parallel toeach other along a second direction substantially perpendicular to thefirst direction. The first and second selection gates may have a linearshape extended in the first direction. The first and second floatinggates may be arranged adjacent to the first and second selection gates,respectively. The first and second floating gates may be overlapped withthe first active region and the second active region, respectively. Thefirst and second floating gates may face each other along the seconddirection. The first floating gate and the second floating gate may haveasymmetrically planar shapes.

In some embodiments, the non-volatile memory device may further includea third well region, a third active region and third and fourth floatinggates. The third well region may have a conductive type substantiallythe same as a conductive type of the first well region. The third activeregion may be defined in the third well region by the device isolationlayer. The third active region may be overlapped with the first andsecond selection gates. The third and fourth floating gates may bearranged adjacent to the first and second selection gates, respectively.The third and fourth floating gates may face each other along the seconddirection. The third floating gate and the fourth floating gate may haveasymmetrically planar shapes along the second direction. The firstfloating gate and the third floating gate may have asymmetrically planarshapes along the first direction. The second floating gate and thefourth floating gate may have asymmetrically planar shapes along thefirst direction.

In some embodiments of the disclosed technology, the plurality of thefloating gates overlapped with the active region may have theasymmetrical planar shapes to prevent a non-uniformity of a couplingratio with respect to each of the floating gates. Thus, the non-volatilememory device may have a uniform threshold voltage, a sufficient marginof a read operation, and improved operational reliability.

Further, a gap between the selection gates and the active region and agap between the floating gates may be sufficiently wide to more improvethe operational reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a unit cell of a non-volatile memory devicebased on some embodiments of the disclosed technology.

FIGS. 2A and 2B examples of a unit cell of a non-volatile memory devicebased on some embodiments of the disclosed technology.

FIG. 3 is an example of a cell array of a non-volatile memory devicebased on some embodiments of the disclosed technology.

FIG. 4A is a cross-sectional view taken along a line A-A′ in FIG. 3 .

FIG. 4B is a cross-sectional view taken along a line B-B′ in FIG. 3 .

DETAILED DESCRIPTION

Features of the technology disclosed in this patent document aredescribed by examples of an image sensing device with reference to theaccompanying drawings. Although a few embodiments of the disclosedtechnology will be discussed, the disclosed technology can beimplemented in various ways beyond the specifics of the examplesdescribed herein.

The disclosed technology can be implemented in some embodiments toprovide a non-volatile memory device as an embedded memory that can beused as an analog trimming device in an SoC device that includes adigital circuit and an analog circuit or an internal memory for storinginstructions and data that are used by the SoC device.

In some implementations, a first conductive type and a second conductivetype may be N-type and P-type, respectively, or vice versa. That is, thenon-volatile memory device based on some example embodiments of thedisclosed technology may include an N-type channel or the P-typechannel. In one example, the first conductive type and the secondconductive type are P-type and N-type, respectively, and thenon-volatile memory device has an N-type channel.

In some implementations, a first direction and a second direction may besubstantially perpendicular to each other. For example, in an X-Ycoordinate, the first direction may be an X-direction and the seconddirection D2 may be a Y-direction.

FIG. 1 is an example of a unit cell of a non-volatile memory devicebased on some embodiments of the disclosed technology. FIG. 1 shows twounit-cells that share a first active region and a second active regionfor the sake of explanation. FIGS. 2A and 2B are examples of a unit cellof a non-volatile memory device based on some embodiments of thedisclosed technology.

In some implementations, the non-volatile memory device may include aplurality of unit cells. Referring to FIGS. 1, 2A and 2B, each of theunit cells may include a first well region PW having a first conductivetype and a second well region NW having a second conductive typeadjacent to the first well region PW. The first well region PW and thesecond well region NW may be formed in a substrate. In someimplementations, two or more unit-cells may share the first well regionPW and the second well region NW. The first well region PW and thesecond well region NW may have a linear shape extending in the seconddirection D2. The first well region PW and the second well region NW maybe parallel to each other along the first direction D1. In animplementation, the first well region PW and the second well region NWmay be spaced apart from each other in the first direction D1. Inanother implementation, the first well region PW may be in directcontact with the second well region NW in the first direction D1.

Each of the first well region PW and the second well region NW mayinclude a first active region AC1 and a second active region AC2 definedby an isolation layer (not shown) in the substrate (not shown). Each ofthe unit cells may share the first active region AC1 and the secondactive region AC2. The first active region AC1 may be used for aprogramming operation and a read operation. The second active region AC2may be used for a programming operation and an erase operation. Thefirst active region AC1 may extend in the second direction D2. Thesecond active region AC2 may extend in the first direction D1.

A first unit cell may include a first selection gate SG1 and a firstfloating gate FG1. The first selection gate SG1 and the first floatinggate FG1 may extend in the first direction D1. The first selection gateSG1 may be spaced apart from the first floating gate FG1 in the seconddirection D2. The first selection gate SG1 may be positioned adjacent tothe first floating gate FG1. The first unit cell and a second unit celladjacent to the first unit cell may share the first active region AC1and the second active region AC2. The second unit cell may include asecond selection gate SG2 and a second floating gate FG2. The secondselection gate SG2 and the second floating gate FG2 may extend in thefirst direction D1. The second selection gate SG2 may be spaced apartfrom the second floating gate FG2 in the second direction D2. The secondselection gate SG2 may be positioned adjacent to the second floatinggate FG2.

The first and second floating gates FG1 and FG2 may include a firstregion 101 and a second region 102. The first region 101 may extend inthe first direction D1. The first regions 101 of the first and secondfloating gates FG1 and FG2 may include a sidewall facing the first andsecond selection gates SG1 and SG2, respectively. The second region 102may extend from a portion of the first region 101 along the seconddirection D2. The second region 102 may overlap with the second activeregion AC2. In some implementations, the first floating gate FG1 and thesecond floating gate FG2 may have different shapes depending on wherethe second region 102 is in contact with the first region 101. Forexample, the second region 102 of the first floating gate FG1 may beconnected to an end of the first region 101 of the first floating gateFG1. In some implementations, the first floating gate FG1 may have avertical linear structure with a protruding horizontal linear structureat an end of the vertical linear structure. In one example, the firstfloating gate FG1 may have an “L” shape. In contrast, the second region102 of the second floating gate FG2 may be connected to a portion of thefirst region 101 of the second floating gate FG2 other than the end ofthe first region 101. In some implementations, the second floating gateFG2 may have has a vertical linear structure with a protrudinghorizontal linear structure. In one example, a cross section of thesecond floating gate FG2 may have a Tonfa shape or a “T” shape.

The first and second selection gates SG1 and SG2 may overlap with thefirst active region AC1. The first and second selection gates SG1 andSG2 may be used as a word line WL. The first and second selection gatesSG1 and SG2 may function to prevent an over-erase condition in the eraseoperation. The first and second floating gates FG1 and FG2 may functionto store logic information. The first and second floating gates FG1 andFG2 may overlap with the first active region AC1 and the second activeregion AC2. Because the second active region AC2 may be used as anactive control gate ACG, the first and second floating gates FG1 and FG2may overlap with the second active region AC2. That is, the secondactive region AC2 may be used as a control gate for controlling thefirst and second floating gates FG1 and FG2 and the first and secondselection gates SG1 and SG2.

Therefore, the first and second floating gates FG1 and FG2 may beelectrically activated in response to a bias applied to the first andsecond selection gates SG1 and SG2, and/or a bias applied to the secondactive region AC2. That is, the first and second floating gates FG1 andFG2 may be coupled in response to the bias applied to the first andsecond selection gates SG1 and SG2 and/or the bias applied to the secondactive region AC2. The first and second floating gates FG1 and FG2 andthe first and second selection gates SG1 and SG2 may be coupled to eachother by a capacitance across surfaces of the first and second floatinggates FG1 and FG2 and the first and second selection gates SG1 and SG2facing each other. That is, the first and second floating gates FG1 andFG2 may be activated by a component of a first capacitor C1 in responseto the bias applied to the first and second selection gates SG1 and SG2.Further, the first and second floating gates FG1 and FG2 and the secondactive region AC2 may be coupled by a capacitance vertically generatedin an overlapping region between the first and second floating gates FG1and FG2 and the second active region AC2. That is, the first and secondfloating gates FG1 and FG2 may be activated by a component of a secondcapacitor C2 in response to the bias applied to the second active regionAC2. Because the first and second floating gates FG1 and FG2 may becoupled by the first and second selection gates SG1 and SG2 and/or thesecond active region AC2, coupling ratios may be different from eachother depending on operational modes. As a result, a disturbance may besuppressed, improving operational reliability.

In FIGS. 2A and 2B, a reference numeral C3 may indicate a thirdcapacitor C3 including the substrate (sub), a gate insulation layer andthe first and second floating gates FG1 and FG2. Although not depictedin the drawings, each of the unit cells may include an insulationstructure that is formed in a gap or space between sidewalls of thefirst and second selection gates SG1 and SG2 and the first and secondfloating gates FG1 and FG2 facing each other. The insulation structuremay include a spacer formed on each of sidewalls of the first and secondselection gates SG1 and SG2 and the first and second floating gates FG1and FG2. The spacer may act as a dielectric layer of the first capacitorC1.

Further, in each of the unit cells, a bit line BL may be electricallyconnected with the first active region AC1 adjacent to the first andsecond floating gates FG1 and FG2. Source lines SL1 and SL2 may beelectrically connected with the first active region AC1 adjacent to thefirst and second selection gates SG1 and SG2. An activation control lineACL may be electrically connected with the second active region AC2.

Hereinafter, the program operation, the erase operation and the readoperation of the unit cell will be discussed with reference to FIGS. 2Aand 2B.

The program operation of the unit cell may use a channel hot electron(CHE). For example, the program operation may include applying apositive pumping voltage to the selection gate SG and the second activeregion AC2, which is used as the active control gate ACG, and applying aprogram voltage and a ground voltage to the bit line BL and the sourceline SL, respectively. The positive pumping voltage may be higher thanthe program voltage. For example, a voltage of about 6V may be appliedto the selection gate SG and the active control gate ACG, and a voltageof about 4.5V may be applied to the bit line BL. The pumping voltage maybe a voltage obtained by raising voltage from a power supply voltageusing, for example, a charge pump.

The erase operation of the unit cell may use a Fowler-Nordheimtunneling. For example, the erase operation may include applying anegative pumping voltage to the selection gate SG, applying a positivepumping voltage to the active control gate ACG, and applying a groundvoltage to the bit line BL and the source line SL. An absolute value ofthe pumping voltage may be higher than an absolute value of the negativepumping voltage. For example, a voltage of about −6V may be applied tothe selection gate SG, and a voltage of about 9V may be applied to theactive control gate ACG.

The read operation of the unit cell may include applying a power supplyvoltage to the selection gate SG, applying a read voltage to the bitline BL, and applying a ground voltage to the active control gate ACGand the source line SL. The read voltage may be higher than the groundvoltage and lower than the power supply voltage. For example, the powersupply voltage may be about −3V and the read voltage may be about 1V.

Hereinafter, the non-volatile memory device of example embodiments maybe illustrated in detail with reference to FIG. 3 .

FIG. 3 is an example of a cell array of a non-volatile memory devicebased on some embodiments of the disclosed technology. FIG. 4A is across-sectional view taken along a line A-A′ in FIG. 3 , and FIG. 4B isa cross-sectional view taken along a line B-B′ in FIG. 3 .

Referring to FIGS. 1, 3, 4A and 4B, the non-volatile memory deviceimplemented based on some embodiments of the disclosed technology mayinclude a cell array 11. The cell array 11 may include a plurality ofsub-arrays 11-1 and 11-2 arranged in rows and columns in a matrix array.Each of the sub-arrays 11-1 and 11-2 may include first to fourth unitcells 10-1 to 10-4. Because the sub-arrays 11-1 and 11-2 may be arrangedin the matrix array, the adjacent sub-arrays 11-1 and 11-2 may besymmetrical about the first and second directions D1 and D2.

Each of the sub-arrays 11-1 and 11-2 may include a second well regionNW, a first well region PW1 and a third well region PW2. The second wellregion NW may be formed in the substrate Sub. The second well region NWmay have the second conductive type. The first well region PW1 may bepositioned over the second well region NW. The first well region PW1 mayhave the first conductive type. The third well region PW2 may bepositioned under the second well region NW. The third well region PW2may have the first conductive type. The first well region PW1, thesecond well region NW and the third well region PW2 may be formed byimplanting ions into the substrate Sub. The first well region PW1 andthe third well region PW2 may be formed by implanting P type impuritiessuch as boron (B) into the substrate Sub. The second well region NW maybe formed by implanting N type impurities such as phosphorus (P),arsenic (As), etc. The first well region PW1, the second well region NWand the third well region PW2 may have a linear planar shape extended inthe second direction D2. In an implementation, the first well regionPW1, the second well region NW and the third well region PW2 may bespaced apart from each other in the first direction D1, not restrictedwithin a specific structure. In another implementation, the second wellregion NW may be in direct contact with the first well region PW1 andthe third well region PW2, respectively.

The substrate Sub may include a semiconductor substrate. Thesemiconductor substrate Sub may include monocrystalline silicon. Forexample, the substrate Sub may include a bulk silicon substrate, asilicon-on-insulator (SOI) substrate including a supporting substrate,an insulation layer and a monocrystalline silicon layer sequentiallystacked, etc.

Each of the first well region PW1 and the third well region PW2 mayinclude a first active region AC1 defined by an isolation layer 103 inthe substrate Sub. The first active region AC1 may be used for theprogram operation and the read operation. The first active region AC1may have a linear planar shape extended in the second direction D2. Byway of example, FIG. 3 shows one first active region AC1 in each of thefirst well region PW1 and the third well region PW2. In anotherimplementation, each of the first well region PW1 and the third wellregion PW2 may include more than one first active regions AC1. Forexample, each of the first well region PW1 and the third well region PW2may include two first active regions AC1 spaced apart from each other inthe first direction D1.

The second well region NW may include a second active region AC2 definedby the isolation layer 103. The second active region AC2 may be used forthe program operation and the erase operation. That is, the secondactive region AC2 may be used as the active control gate ACG. Thus, thecoupling ratios may be different from each other depending on theoperational modes, suppressing the disturbance and improving theoperational reliability. The second active region AC2 may extend in thefirst direction D1. The second active region AC2 extending in the firstdirection D1 may prevent or reduce interference and punch-through effectbetween the first and second selection gates SG1 and SG2, and the secondactive region AC2. Here, the punch-through effect may include anundesired electrical connection between the first and second selectiongates SG1 and SG2, and the second active region AC2.

The isolation layer 103 may be formed by a shallow trench isolation(STI) process. The isolation layer 103 may include an insulationmaterial. The isolation layer 103 may have a depth measured from the topsurface of the substrate Sub. In an implementation, the depths of thefirst well region PW1, the second well region NW and the third wellregion PW2 may be deeper than that of the isolation layer 103. Inanother implementation, the depth of the isolation layer 103 may besubstantially equal to or deeper than the depths of the first wellregion PW1, the second well region NW and the third well region PW2.

Each of the sub-arrays 11-1 and 11-2 may include the first selectiongate SG1 and the second selection gate SG2 formed at the substrate Sub.The first selection gate SG1 may be used as a word line of the firstunit cell 10-1 and the third unit cell 10-3. The second selection gateSG2 may be used as a word line of the second unit cell 10-2 and thefourth unit cell 10-4. Each of the first selection gate SG1 and thesecond selection gate SG2 may function to prevent the over-erase in theerase operation. The first selection gate SG1 and the second selectiongate SG2 may be spaced apart from each other in the second direction D2.Further, the selection gate SG1 and the second selection gate SG2 may beparallel to each other. A gap (g1) between the second active region AC2and the first selection gate SG1 may be identical or similar to a gap(g2) between the second active region AC2 and the second selection gateSG2. The gaps (g1 and g2) are sufficiently wide to effectively preventthe interference and the punch-through effect between the second activeregion AC2 and the first and second selection gates SG1 and SG2.

Each of the sub-arrays 11-1 and 11-2 may include a first floating gateFG1, a second floating gate FG2, a third floating gate FG3 and a fourthfloating gate FG4 structured to be coupled to the second active regionAC2. In some implementations, the first to fourth floating gates FG1 toFG4 are arranged in a longitudinal direction of the second active regionAC2. In some implementations, the first and third floating gates FG1 andFG3 are arranged at one side of the second active region AC2 thatextends in the longitudinal direction of the second active region AC2,and the second and fourth floating gates FG2 and FG4 are arranged at theother side of the second active region AC2 that extends in thelongitudinal direction of the second active region AC2. Each of thefirst to fourth floating gates FG1 to FG4 includes a branch structuredto extend toward the second active region AC2. The branches of the firstto fourth floating gates FG1 to FG4 are coupled to the second activeregion AC2 and are spaced apart from one another. In one example, thebranches may include the second regions 102 of the first and fourthfloating gates FG1 and FG4. In some implementations, the first to fourthfloating gates FG1, FG2, FG3 and FG4 may be structured to partiallyoverlap with the second active region AC2. The first to fourth floatinggates FG1, FG2, FG3 and FG4 may correspond to the first to fourth unitcells 10-1, 10-2, 10-3 and 10-4, respectively. The first to fourthfloating gates FG1, FG2, FG3 and FG4 may store electrical chargecorresponding to one or more bits of information. The first to fourthfloating gates FG1, FG2, FG3 and FG4 may overlap with the first activeregion AC1 and the second active region AC2. The first floating gate FG1and the third floating gate FG3 may be arranged adjacent to the firstselection gate SG1 and may be spaced apart from the first selection gateSG1 by a gap 110. The second floating gate FG2 and the fourth floatinggate FG4 may be arranged adjacent to the second selection gate SG2 andmay be spaced apart from the second selection gate SG2 by the gap 110.The gap 110 may be filled with an insulation structure 112. Theinsulation structure 112 may include a spacer formed on a sidewall ofeach of the selection gates SG1 and SG2 and the floating gates FG1-FG4.

The second region 102 of the first and fourth floating gates FG1 and FG4may be connected to one end or the other end of the first region 101 ofthe first and fourth floating gates FG1 and FG4 so that the first andfourth floating gates FG1 and FG4 may have an “L” shape. In contrast,the second region 102 of the second and third floating gates FG2 and FG3may be connected to one end or the other end of the first region 101 ofthe second and third floating gates FG2 and FG3 so that a horizontalcross section of each of the second and third floating gates FG2 and FG3may have a vertical linear structure with a protruding horizontal linearstructure. In one example, cross sections of the second and thirdfloating gates FG2 and FG3 may have Tonfa shapes or “T” shapes. Thus,the first floating gate FG1 and the third floating gate FG3 facing eachother in the first direction D1 may have asymmetrically shapes. Further,as illustrated in the plan view on FIG. 3 , the first floating gate FG1and the second floating gate FG2 facing each other in the seconddirection D2 may have asymmetrically shapes. The third floating gate FG3and the fourth floating gate FG4 facing each other in the seconddirection D2 may have asymmetrically shapes. The fourth floating gateFG4 and the second floating gate FG2 facing each other in the firstdirection D1 may have asymmetrically shapes. These shapes of thefloating gates FG1, FG2, FG3 and FG4 may prevent the interferencebetween the floating gates FG1, FG2, FG3 and FG4 and provide the secondcapacitor C2 in each of the unit cells 10-1-10-4 with a uniformcapacitance to prevent or reduce discrepancy between the coupling ratioswith respect to the floating gates FG1-FG4. Thus, each of the unit cells10-1-10-4 may include floating gates FG1-FG4 that are asymmetrical fromeach other and have branches spaced apart from each other to improve thethreshold voltage uniformity. As a result, the reliability of the readoperation may be improved.

In some implementations, each of the first to fourth floating gatesFG1-FG4 may include the first region 101 and the second region 102. Thefirst region 101 may have a structure that extends in the firstdirection D1. The second region 102 may protrude or extend from thefirst region 101 in the second direction D2. The first region 101 maypartially overlap with the first active region AC1. The second region102 may partially overlap with the second active region AC2. In orderfor the first capacitor C1 in FIG. 2A and FIG. 2B to have a sufficientlyhigh capacitance, the first region 101 may have a length longer than alength of the second region 102. Further, in order for the secondcapacitor C2 of each of the unit cells 10-1-10-4 in FIG. 2A and FIG. 2Bto have uniform capacitance, the second region 102 may be structured tocross the second active region AC2. In one example, the second region102 may be structured to cross the isolation layer 103 and the secondactive region AC2 along the second direction D2. Thus, the second activeregion AC2 and the first to fourth floating gates FG1-FG4 may havesubstantially the same overlapped area.

The second regions 102 of the first to fourth floating gates FG1-FG4 maybe spaced apart from each other in the first direction D1. The secondregion 102 may be located at a central portion of the second activeregion AC2. The second regions 102 of the second and third floatinggates FG2 and FG3 may be positioned at one edge and the other edge ofthe second active region AC2, respectively. The gap S between the secondactive region AC2 and the first to fourth floating gates FG1-FGF4 may beidentical or similar.

The first active region AC1 in each of the sub-arrays may include afirst junction region 104 formed between the first floating gate FG1 andthe second floating gate FG2, and between the third floating gate FG3and the fourth floating gate FG4. Further, the first active region AC1may include a second junction region 106 and a third junction region108. The second junction region 106 may be formed in the first activeregion AC1 adjacent to the first and second selection gates SG1 and SG2.The third junction region 108 may be formed under the insulationstructure 112 in the gap 110. The first, second and third junctionregions 104, 106 and 108 may include impurity regions formed byimplanting the second conductive type impurities into the first activeregion AC1. The first junction region 104 and the second junction region106 may have an LDD structure. The third junction region 108 mayfunction as to electrically connect an induced channel by the selectiongate and the floating gate with the first active region AC1. The firstjunction region 104 may be connected to the bit line BL. A portion ofthe first junction region 104 between the first floating gate FG1 andthe second floating gate FG2 and a portion of the first junction region104 between the third floating gate FG3 and the fourth floating gate FG4may be connected to different bit lines BL. The second junction region106 may be connected to the source line SL. A portion of the secondjunction region 106 adjacent to the first selection gate SG1 and aportion of the second junction region 106 adjacent to the secondselection gate SG2 may be electrically connected to different sourcelines SL.

The second active region AC2 in each of the sub-arrays 11-1 and 11-2 maybe electrically connected with an activation control line ACL parallelto the bit line BL. Although not depicted in the drawings, the secondactive region AC2 may further include an impurity region for reducing acontact resistance between the activation control line ACL and thesecond active region AC2. The impurity region may be formed byimplanting the second conductive type impurities. The impurity regionmay have a doping concentration higher than a doping concentration ofthe impurity region in the second well region NW.

In some embodiments of the disclosed technology, the plurality of thefloating gates FG1-FG4 overlapping with the second active region AC2 mayhave asymmetrical shapes to prevent or reduce discrepancy between thecoupling ratios with respect to the floating gates FG1-FG4. Thus, thenon-volatile memory device may have a uniform threshold voltage,improving the reliability of a read operation.

Further, gaps (g1, g2) between the selection gates SG1 and SG2 and thesecond active region AC2 and a gap(S) between the floating gates FG1-FG4may be sufficiently wide to more improve the operational reliability.

The technical features disclosed in this patent document can beimplemented in various configurations or ways and the disclosedembodiments are merely examples of certain implementations. Variationsand enhancements of the disclosed embodiments and other embodiments canbe made based on what is disclosed and/or illustrated in this patentdocument.

What is claimed is:
 1. A memory device comprising: a substrate includingan active region; and a first floating gate, a second floating gate, athird floating gate and a fourth floating gate formed on the substrate,arranged to partially overlap with the active region, wherein the firstfloating gate and the third floating gate are arranged in a firstdirection at one side of the active region and asymmetrical about acenter of the active region, and the second floating gate and the fourthfloating gate are arranged in the first direction at another side of theactive region and asymmetrical about the center of the active region,and wherein the first floating gate and the second floating gate arearranged to face each other in a second direction perpendicular to thefirst direction, and the first floating gate is asymmetrical from thesecond floating gate, and the third floating gate and the fourthfloating gate are arranged to face each other in the second direction,and the third floating gate is asymmetrical from the fourth floatinggate.
 2. The memory device of claim 1, wherein the third floating gateand the fourth floating gate facing each other in the second directionare asymmetrical about an axis passing through the center of the activeregion in the first direction, and the fourth floating gate and thesecond floating gate facing each other in the first direction areasymmetrical about an axis passing through the center of the activeregion in the second direction.
 3. The memory device of claim 1, whereinthe active region is structured to extend in the first direction, thefirst floating gate and the fourth floating gate are spaced apart fromeach other, and the second floating gate and the third floating gateoverlap with one edge portion and the other edge portion of the activeregion, respectively, and the first floating gate overlaps with aportion of the active region between the one edge and the center of theactive region, and the fourth floating gate overlaps with anotherportion of the active region between the other edge and the center ofthe active region.
 4. The memory device of claim 3, wherein the portionsof the active regions where the first to fourth floating gatesoverlapping with the active region are arranged in the first directionand spaced apart by a gap.
 5. The memory device of claim 1, wherein thefirst floating gate and the fourth floating gate have L shapes, and ahorizontal cross section of each of the second floating gate and thethird floating gate has a vertical linear structure with a protrudinghorizontal linear structure.
 6. The memory device of claim 1, whereineach of the first to fourth floating gates comprises a first regionhaving a linear shape extending in the first direction and a secondregion having a linear shape extending from the first region in thesecond direction.
 7. The memory device of claim 6, wherein each firstregion in each of the first to fourth floating gates has a length longerthan a length of each second region in each of the first to fourthfloating gates.
 8. The memory device of claim 6, wherein the secondregion is structured to cross the active region and partially overlapwith the active region, and overlapped areas between the active regionand the first to fourth floating gates are substantially equal to eachother.
 9. The memory device of claim 1, wherein the active region isused as an active control gate.
 10. A memory device comprising: asubstrate; first and second well regions formed in the substrate andhaving different conductive types, the first and second well regionsarranged parallel to each other in a first direction; an isolation layerformed in the substrate to define a first active region and a secondactive region in each of the first and second well regions; first andsecond selection gates formed on the substrate and structured to overlapwith the first active region, the first and second selection gatesarranged parallel to each other in a second direction substantiallyperpendicular to the first direction, and the first and second selectiongates having a linear shape extending in the first direction; and firstand second floating gates arranged adjacent to the first and secondselection gates, respectively, the first and second floating gatesoverlapping with the first active region and the second active region,and the first and second floating gates facing each other in the seconddirection, wherein the first floating gate and the second floating gateface each other in the second direction and are asymmetrical from eachother.
 11. The memory device of claim 10, wherein the first selectiongate and the first floating gate, and the second selection gate and thesecond floating gate have sidewalls facing each other in the seconddirection, and an insulation structure is formed between the sidewalls.12. The memory device of claim 10, wherein the second active regionstructured to extend in the first direction, a distance between thefirst selection gate and the second active region in the seconddirection is substantially the same as a distance between the secondselection gate and the second active region in the second direction. 13.The memory device of claim 10, wherein the second active region is usedas an active control gate, a positive pumping voltage is applied to thesecond active region in a program operation and an erase operation, andthe positive pumping voltage in the erase operation is higher than thepositive pumping voltage in the program operation.
 14. The memory deviceof claim 10, wherein a cross section of the first floating gate has an Lshape, and a cross section of the second floating gate has a verticallinear structure with a protruding horizontal linear structure.
 15. Thememory device of claim 10, wherein each of the first and second floatinggates comprises a first region having a linear shape extending in thefirst direction and a second region having a linear shape extending fromthe first region in the second direction.
 16. The memory device of claim15, wherein the first region has a length longer than a length of thesecond region, the second region is structured to cross the secondactive region and partially overlap with the second active region, andoverlapped areas between the second active region and the first andsecond floating gates are substantially equal to each other.
 17. Thememory device of claim 10, further comprising: a third well regionformed at the substrate, the third well region having a conductive typesubstantially the same as the conductive type of the first well region;a third active region defined in the third well region by the isolationlayer, the third active region overlapping with the first selection gateand the second selection gate; and third and fourth floating gatesarranged adjacent to the first and second selection gates, respectively,the third and fourth floating gates overlapping with the third activeregion and the second active region, and the third and fourth floatinggates facing each other in the second direction, wherein the thirdfloating gate and the fourth floating gate face each other in the seconddirection and are asymmetrical from each other.
 18. The memory device ofclaim 17, wherein the first floating gate and the third floating gateface each other in the first direction and are asymmetrical from eachother.
 19. The memory device of claim 17, wherein the second floatinggate and the fourth floating gate face each other in the first directionand are asymmetrical from each other.
 20. The memory device of claim 17,wherein overlapped areas in the first direction between the secondactive region and the first to fourth floating gates are substantiallyequal to each other.